Nice! Thank you thomaso! I am gonna try this with the Piston Honda wavetables as above mentioned.
To import into the M, Vlad gave an explanation here:
Serum .256 files (8-bit exports) fits ideally. Just export from Serum, rename to wtslotXX where XX is between 00-31, i.e. number of the slot in the M. Then copy the file to the SD Card in the root directory, choose in the Option slot, and skip settings. Then go to the Operations and select Load user wavetable.